The used drive in conjunction with the PCMCIA- or USB-Contoller is not so important due to the fact, that the driver in the BIOS has to enable the Controller first.
There is a generic CD-Rom driver implemented into the BIOS for the attached Drive .

I have an m200 and have had problems booting from external dvd drives.

A Full size pioneer DVD-RW will not boot but a slimline LaCIe (Design by FA porsche) this uses aan NEC ND6500A drive apparently however it will only boot if you use the external AC adaptor. Using the usb power lead lets the drive read and possibly write DVD's but not boot from them.